(CNN) -

Country music star Carrie Underwood and husband Mike Fisher took to Twitter Monday to make an announcement: They are expecting their first child.

In a riddle of sorts, Underwood tweeted a picture of herself holding her two dogs, with the dogs sporting T-shirts that read "I'm going to be a big brother" on one and "big sister" on the other.

The tweet reads "In honor of 'Labor' Day ... Ace & Penny would like to make an announcement. Their parents couldn't be happier! "

Her husband, Mike Fisher, an NHL player, tweeted more directly: "We haven't picked names yet, but it's looking like Fly is gonna fly."

The 31-year old Underwood was the "American Idol" champion in 2004 and has been releasing hits ever since.

In June, the platinum-selling singer took home a CMT Music Award for video of the year, for her hit "See You Again." It was the fifth time Underwood snagged the award and her third win in a row.